5-HT1 receptor

In vitro activity: Rizatriptan Benzoate (also known as MK-462 Benzoate) is a brand-new, highly effective, and selective agonist at serotonin 5-HT1B and 5-HT1D receptors; it may be utilized to treat acute attacks of migraines.

Rizatriptan blocks the release of CGRP in anesthetized guinea pigs by acting on 5-HT(1D) receptors on perivascular trigeminal nerves, thereby inhibiting neurogenic vasodilation. In anesthetized guinea pigs, rizatriptan causes a brief decrease in dural blood vessel diameter, which returns to baseline levels in 10 minutes.[1] The dural plasma protein extravasation that results from intense electrical stimulation of the trigeminal ganglion is markedly inhibited by rizatriptan. In rats under anesthesia, ritariptan dramatically lowers electrically induced dural vasodilation.[2] It has been observed that Rizatriptan Benzoate can downregulate SP gene expression in the rat midbrain by significantly reducing SP mRNA levels in the midbrains of both normal and model group rats. In rat models of migraine, rizatriptan benzoate diminishes the analgesic effects of the endogenous pain modulatory system by significantly lowering midbrain PENK mRNA expression, which in turn lowers midbrain met-enkephalin and leu-enkephalin levels.[3] The number of Fos-like immunoreactive neurons in the caudal part and raphe magnus nucleus of the spinal trigeminal nucleus decreased in conscious rats, while the number increased in the periaqueductal gray and remained unchanged in the ventromedial hypothalamic and mediodorsal thalamus nuclei. These findings were observed in rats administered Riztriptan Benzoate.[4] Rizatriptan Benzoate significantly lowers the rats' head-flicking frequency. Additionally, compared to when treatment is not received, rizatriptan benzoate significantly shortens the duration of grooming behavior by almost two times. [5]

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These studies investigated the pharmacology of neurogenic dural vasodilation in anaesthetized guinea-pigs. Following introduction of a closed cranial window the meningeal (dural) blood vessels were visualized using intravital microscopy and the diameter constantly measured using a video dimension analyser. Dural blood vessels were constricted with endothelin-1 (3 microg kg(-1), i.v.) prior to dilation of the dural blood vessels with calcitonin gene-related peptide (CGRP; 1 microg kg(-1), i.v.) or local electrical stimulation (up to 300 microA) of the dura mater. In guinea-pigs pre-treated with the CGRP receptor antagonist CGRP((8-37)) (0.3 mg kg(-1), i.v.) the dilator response to electrical stimulation was inhibited by 85% indicating an important role of CGRP in neurogenic dural vasodilation in this species. Neurogenic dural vasodilation was also blocked by the 5-HT(1B/1D) agonist rizatriptan (100 microg kg(-1)) with estimated plasma levels commensurate with concentrations required for anti-migraine efficacy in patients. Rizatriptan did not reverse the dural dilation evoked by CGRP indicating an action on presynaptic receptors located on trigeminal sensory fibres innervating dural blood vessels. In addition, neurogenic dural vasodilation was also blocked by the selective 5-HT(1D) agonist PNU-142633 (100 microg kg(-1)) but not by the 5-HT(1F) agonist LY334370 (3 mg kg(-1)) suggesting that rizatriptan blocks neurogenic vasodilation via an action on 5-HT(1D) receptors located on perivascular trigeminal nerves to inhibit CGRP release. This mechanism may underlie one of the anti-migraine actions of the triptan class exemplified by rizatriptan and suggests that the guinea-pig is an appropriate species in which to investigate the pharmacology of neurogenic dural vasodilation.[1]

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These studies in anaesthetised rats showed, using intravital microscopy, that the novel anti-migraine agent, Rizatriptan, significantly reduced electrically stimulated dural vasodilation but had no effect on increases in dural vessel diameter produced by exogenous substance P or calcitonin gene-related peptide (CGRP). Rizatriptan also significantly inhibited dural plasma protein extravasation produced by high intensity electrical stimulation of the trigeminal ganglion. We suggest that rizatriptan inhibits the release of sensory neuropeptides from perivascular trigeminal nerves to prevent neurogenic vasodilation and extravasation in the dura mater. These prejunctional inhibitory effects may be involved in the anti-migraine action of rizatriptan.[2]

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The present study utilized a nitroglycerin-induced rat model of migraine to detect the effects of Rizatriptan benzoate on proenkephalin and substance P gene expression in the midbrain using real-time quantitative polymerase chain reaction and investigate whether rizatriptan benzoate can regulate the endogenous pain modulatory system. The results showed that rizatriptan benzoate significantly reduced expression of the mRNAs for proenkephalin and substance P. Rizatriptan benzoate may inhibit the analgesic effect of the endogenous pain modulatory system.[3]

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Fos expression in the brain was systematically investigated by means of immunohistochemical staining after electrical stimulation of the dura mater surrounding the superior sagittal sinus in conscious rats. Fos-like immunoreactive neurons are distributed mainly in the upper cervical spinal cord, spinal trigeminal nucleus caudal part, raphe magnus nucleus, periaqueductal gray, ventromedial hypothalamic nucleus, and mediodorsal thalamus nucleus. With the pre-treatment of intraperitoneal injection of Rizatriptan benzoate, the number of Fos-like immunoreactive neurons decreased in the spinal trigeminal nucleus caudal part and raphe magnus nucleus, increased in the periaqueductal gray, and remained unchanged in the ventromedial hypothalamic nucleus and mediodorsal thalamus nucleus. These results provide morphological evidence that the nuclei described above are involved in the development and maintenance of the trigeminovascular headache.[4]

SYBR green real-time quantitative PCR [3]
Twenty-microliter reactions comprised 10 μL of SYBR Premix Ex Taq™, 0.4 μL of upstream and downstream primers (10 μM), 0.4 μL of ROX Reference Dye, 2.0 μL of cDNA, and 6.8 μL of dH2O. Different concentrations of plasmid standard samples (1.2 × 103−1.2 × 109) copies/μL were processed by quantitative PCR. Each sample was run in triplicate. Reaction conditions were as follows: 94°C pre-denaturation for 2 minutes, 94°C denaturation for 30 seconds, 62°C annealing for 30 seconds, 72°C extension for 30 seconds, for a total of 40 cycles. Fluorescence signals were measured at the end of annealing in each cycle with the critical point for measurement defined during PCR amplification, i.e. the value of the threshold cycle corresponding to the inflection point of fluorescence signals entering the exponential growth phase above background level. A melting curve analysis was performed in a pattern of 95°C for 15 seconds, 60°C for 20 seconds, and 95°C for 15 seconds.

In preliminary experiments it was found that, following introduction of the cranial window, the dural blood vessels typically were observed to be maximally dilated, so that electrical stimulation of the cranial window produced little if any increase in diameter. It was therefore necessary to preconstrict the dural vessels with intravenously administered endothelin-1 (ET-1, 3 μg kg−1) which produced an approximate 50% reduction in dural blood vessel diameter (unpublished observations). Following administration of endothelin-1 (3 μg kg−1, i.v.) dural vasodilation was reliably evoked approximately 3 min later by intravenous rat-αCGRP (1 μg kg−1) or electrical stimulation of the cranial window (250–300 μA, 5-Hz, 1 ms for 10 s) and expressed as percentage increase in dural blood vessel diameter±s.e.mean from baseline. Rizatriptan benzoate (0.01–1 mg kg−1), PNU142,633 (0.01–1 mg kg−1) or LY334370 (3 mg kg−1) were administered intravenously 12 min before administration of ET-1 whereas human-αCGRP(8–37) (0.3 mg kg−1) was given 2 min prior to ET-1. Statistical comparisons between drug and vehicle treated rats were made by t-tests (BMDP statistical software) and P<0.05 was considered significant. [1]

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Migraine model establishment and interventions [3]
Rizatriptan benzoate control and treatment groups were intragastrically perfused with rizatriptan benzoate, 1 mg/kg per day (according to the adult daily dose), and normal control and model groups were perfused with normal saline 2 mL per day. After 7 days, nitroglycerin (10 mg/kg) was subcutaneously injected into the buttocks of the rizatriptan benzoate treatment and model groups to induce migraine. Normal saline (2 mL/kg) was injected into the normal control and rizatriptan benzoate control groups.

Absorption, Distribution and Excretion
Rizatriptan is rapidly absorbed after oral administration (approximately 90%); however, due to extensive first-pass metabolism, the mean oral absolute bioavailability of rizatriptan tablets is approximately 45%. The time to peak concentration (Tmax) is approximately 1 to 1.5 hours. Migraine does not appear to affect the absorption or pharmacokinetics of rizatriptan. Food has no significant effect on the bioavailability of rizatriptan but delays the time to peak concentration by 1 hour. In clinical trials, administration of rizatriptan was not affected by food. The bioavailability and time to peak concentration (Cmax) of rizatriptan are similar after administration of both tablets and orally disintegrating tablets. Nevertheless, the absorption rate of orally disintegrating tablets is slightly slower, with a maximum delay of 0.7 hours in reaching peak concentration. The AUC of rizatriptan is approximately 30% higher in women than in men. No accumulation was observed with multiple dosings. Following a single oral dose of 10 mg of 14C-rizatriptan, 82% of the total radioactivity was recovered in urine and 12% in feces within 120 hours. Rizatriptan accounts for approximately 17% of circulating plasma radioactivity after oral administration. Approximately 14% of the oral dose is excreted unchanged in urine, and 51% is excreted as an indoleacetic acid metabolite, indicating significant first-pass metabolism. The mean volume of distribution was approximately 140 liters in male subjects and approximately 110 liters in female subjects. An earlier study in healthy subjects reported a plasma clearance rate of 1042 mL/min in men and 821 mL/min in women; however, this difference in clearance rate was considered clinically insignificant.

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Metabolism/Metabolites
Rizatriptan is primarily metabolized by monoamine oxidase A (MAO-A)-mediated oxidative deamination to triazole methylindole-3-acetic acid, which is pharmacologically inactive. N-Monodemethylrizatriptan is a minor metabolite with pharmacological activity comparable to the parent compound. The plasma concentration of N-monodemethylrizatriptan is approximately 14% of that of the parent compound, and both metabolites are eliminated at similar rates. Other metabolites with lower pharmacological activity include N-oxides, 6-hydroxy compounds, and sulfate conjugates of 6-hydroxy metabolites. Rizatriptan is metabolized by monoamine oxidase A isoenzyme (MAO-A) to the inactive indoleacetic acid metabolite. Several other inactive metabolites are also generated. An active metabolite, N-monodemethylrizatriptan, has been detected in plasma with pharmacological activity similar to the parent compound, but at a lower concentration (14%). Elimination pathway: Approximately 14% of the oral dose of rizatriptan is excreted unchanged in the urine, and 51% is excreted as an indoleacetic acid metabolite, indicating significant first-pass metabolism. Half-life: 2-3 hours. The plasma half-life of rizatriptan in both men and women is 2 to 3 hours.

Effects During Pregnancy and Lactation
◉ Overview of Use During Lactation
Rizatriptan has low concentrations in breast milk and a relatively short half-life in milk. The dose ingested by the infant is very small and unlikely to affect a breastfeeding infant. Nipple pain, burning sensation, and breast pain have been reported after taking sumatriptan and other triptans. This is sometimes accompanied by a decrease in milk production.
◉ Effects on Breastfed Infants
As of the revision date, no relevant published information was found.
◉ Effects on Lactation and Breast Milk
A review of four European adverse reaction databases found 26 reports of nipple pain, burning sensation, breast pain, breast engorgement, and/or let-down pain in breastfeeding women taking triptans. The pain was sometimes severe and occasionally led to a decrease in milk production. The pain usually subsides gradually as the drug is metabolized. The authors suggest that triptans may cause vasoconstriction in the breast, nipple, and arteries surrounding the alveoli and ducts, leading to pain and painful milk ejection reflex.

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Protein Binding
Rizatriptan has an extremely low binding rate to plasma proteins (14%).

[1]. Br J Pharmacol. 2001 Aug;133(7):1029-34.

[2]. Eur J Pharmacol. 1997 Jun 5;328(1):61-4.

[3]. Neural Regen Res. 2012 Jan 15;7(2):131-5.

[4]. Brain Res. 2011 Jan 7:1367:340-6.

[5]. Brain Res. 2011 Jan 12:1368:151-8.

Rizatriptan belongs to the tryptamine class of drugs. It is a serotonergic agonist, vasoconstrictor, and anti-inflammatory drug. Its function is related to N,N-dimethyltryptamine. Rizatriptan is a second-generation triptan and a selective 5-HT1B and 5-HT1D receptor agonist. Rizatriptan is used to treat migraines and was first approved in the United States in 1998. Rizatriptan is available in oral tablets, orally disintegrating tablets (thin tablets), and oral films. Rizatriptan is a 5-HT1B and 5-HT1D receptor agonist. The mechanism of action of rizatriptan is as a 5-HT1B and 5-HT1D receptor agonist. Rizatriptan is only detected in individuals who have taken the drug. It is a triptan used to treat migraines. It is a selective serotonin type 1 receptor agonist. The anti-migraine effects of triptans involve three distinct pharmacological mechanisms: (1) stimulation of presynaptic 5-HT1D receptors, thereby inhibiting dural vasodilation and inflammation; (2) direct inhibition of trigeminal nucleus cell excitability by activating 5-HT1B/1D receptors in the brainstem; and (3) vasoconstriction of the meninges, dura mater, cerebral vessels, or pia mater due to activation of 5-HT1B receptors in blood vessels. See also: rizatriptan benzoate (salt form); rizatriptan sulfate (salt form).

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Drug Indications
Rizatriptan is indicated for the treatment of a confirmed acute attack of migraine with or without aura. Rizatriptan is not indicated for the prophylactic treatment of migraine or for the treatment of cluster headaches. In Canada, rizatriptan is approved for use in adults. In the United States, oral tablets are approved for patients aged 6 years and older, and oral film formulations are approved for patients aged 12 years and older and weighing 40 kg or more.
Treatment of Migraines

Mechanism of Action

The pathophysiology of migraines involves multiple physiological and molecular processes. Dilation of intracranial and extracranial blood vessels (especially those supplying the dura mater) is associated with migraine pain. Activation of the trigeminal vascular system leads to the release of vasoactive neuropeptides (such as substance P, calcitonin gene-related peptide (CGRP), and neurokinin A) by the trigeminal nerve, which innervates intracranial blood vessels and the dura mater. Vasoactive neuropeptides can cause peripheral perivascular inflammation and vasodilation. Migraine-related nausea and vomiting are thought to result from activation of central and nociceptive sensory neurons projecting to autonomic brainstem nuclei as well as higher subcortical and cortical pain processing centers. Imbalances in serotonin (5-HT) levels have also been confirmed: 5-HT binds to 5-HT_sub>1B and 5-HT_sub>1D receptors, promoting trigeminal neuronal firing and vasoconstriction. Rizatriptan is a selective agonist of 5-HT1B and 5-HT1D receptors on intracranial vessels and the sensory nerve of the trigeminal nerve, exhibiting high affinity for these receptors. The exact mechanism of action of rizatriptan is not fully elucidated. However, several documented pharmacological effects of rizatriptan may contribute to its anti-migraine efficacy. Rizatriptan causes intracranial and extracranial vasoconstriction, which is thought to be primarily mediated through 5-HT1B receptors. Rizatriptan also inhibits nociceptive neurotransmission in the trigeminal neuralgia pathway. It attenuates the release of vasoactive neuropeptides from the trigeminal nerve, which is thought to be mediated through neurogenic and central 5-HT1D receptors. Animal studies have shown that rizatriptan inhibits neurogenic dural vasodilation and plasma protein exudation. Rizatriptan benzoate belongs to the tryptamine class of drugs. Rizatriptan benzoate is the benzoate form of rizatriptan, a triptan drug with anti-migraine effects. Rizatriptan benzoate selectively binds to and activates 5-HT1B receptors expressed in intracranial arteries, as well as 5-HT1D receptors located at the sensory terminals of the trigeminal nerve in the peridural space and the central terminals of the sensory nuclei in the brainstem. Receptor binding leads to intracranial vasoconstriction and blockage of nociceptive transmission, thereby relieving migraines. Rizatriptan benzoate may also relieve migraines by inhibiting the release of pro-inflammatory neuropeptides. See also: Rizatriptan (containing the active ingredient). This study demonstrates that in anesthetized guinea pigs, electrical stimulation of the dura mater induces neurogenic vasodilation of pre-constricted dural vessels, and this vasodilation is mediated by calcitonin gene-related peptide (CGRP) released from trigeminal nerve fibers. In addition, rizatriptan, at clinically relevant doses, can also block neurogenic dural vasodilation by acting on presynaptic 5-HT1D receptors, but cannot block CGRP-induced dural vasodilation. This is because the 5-HT1D agonist PNU142,633 can also block neurogenic dural vasodilation, while the 5-HT1F agonist LY334370 cannot. This study suggests that guinea pigs may be a suitable animal model for studying the pharmacology of neurogenic dural vasodilation, and the data can be extrapolated to humans. [1]

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Opioid peptides and opioid receptor agonists exert potent analgesic effects by inhibiting neuronal pain-induced discharges and activating the descending inhibitory system of pain regulation. Enkephalins are divided into two forms according to their structure: methionine enkephalins and leucine enkephalins. They are both derived from a single precursor, namely PENK. The results of this study showed that there was no significant difference in the expression level of PENK in the midbrain between the model group and the normal control group, indicating that migraine does not directly affect the expression of PENK in the midbrain. However, the effect of migraine on opioid peptide expression still needs further investigation. Rizatriptan benzoate significantly reduced the expression of PENK mRNA in the midbrain, and reduced the levels of methionine enkephalin and leucine enkephalin in the midbrain, thereby weakening the analgesic effect of the endogenous pain regulation system. In addition, previous studies have shown that SP can stimulate the release of enkephalin from the periaqueductal gray matter. In this study, rizatriptan benzoate reduced the expression of SP and PENK mRNA in the midbrain. However, whether there is a correlation between these two reductions needs further investigation. In summary, rizatriptan benzoate reduced the expression of SP and PENK mRNA in the midbrain, which may have inhibited the analgesic effect of the endogenous pain regulation system. [3]

C15H19N5

269.35

269.164

C, 66.89; H, 7.11; N, 26.00

144034-80-0

Rizatriptan-d6 benzoate; 1216984-85-8; 144034-80-0; 159776-67-7 (sulfate)

5078

Typically exists as solid at room temperature

1.21g/cm3

504.8ºC at 760mmHg

178-180ºC

259.1ºC

2.58E-10mmHg at 25°C

1.911

1

3

5

20

309

0

CN(C)CCC1=CNC2=C1C=C(C=C2)CN3C=NC=N3

ULFRLSNUDGIQQP-UHFFFAOYSA-N

InChI=1S/C15H19N5/c1-19(2)6-5-13-8-17-15-4-3-12(7-14(13)15)9-20-11-16-10-18-20/h3-4,7-8,10-11,17H,5-6,9H2,1-2H3

N,N-dimethyl-2-[5-(1,2,4-triazol-1-ylmethyl)-1H-indol-3-yl]ethanamine

MK-462; MK 462; 144034-80-0; MK 462 free base; 2-(5-((1H-1,2,4-Triazol-1-yl)methyl)-1H-indol-3-yl)-N,N-dimethylethanamine; rizatriptanum; 1H-Indole-3-ethanamine, N,N-dimethyl-5-(1H-1,2,4-triazol-1-ylmethyl)-; N,N-dimethyl-2-[5-(1,2,4-triazol-1-ylmethyl)-1H-indol-3-yl]ethanamine; Risatriptan; Rizatriptan

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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 (Please use freshly prepared in vivo formulations for optimal results.)